External Mirrors need to have an aerodynamic rear surface and thus covers need to be smooth and preferably have no surface defects that may create wind noise.
U.S. Pat. No. 5,583,703 in FIG. 4 discloses fastening the rear cover by external screws. This creates an unsightly appearance and a non aerodynamic surface.
Most Mirror constructions overcome this problem by having covers that snap on or are clipped onto the mirror assembly. U.S. Pat. No. 5,621,577 is illustrative of this approach. These are not satisfactory because they can easily be dislodged if the mirror is struck.
U.S. Pat. No. 5,604,644 uses an internal screw for the cover which is accessed by removing the mirror plate.
It is an object of this invention to provide a more satisfactory means of securely fastening the rear cover to the mirror assembly.